The present invention relates to firearms, and in particular, to firearms employing percussion caps to ignite a propellant charge.
In the period between 1807 and 1825, there was developed a percussion firing method to replace the flintlock method for igniting a propellant charge in a firearm.
The basic elements of the percussion firing system are a percussion cap and a nipple communicating with the firearm ignition chamber. The percussion cap is designed to fit snugly over the nipple in a position to be struck by the hammer of the firearm. When struck, an explosive fulminate in the base of the percussion cap produces a quantity of burning gas in the nipple, and this gas is forced under considerable pressure into the ignition chamber of the firearm, igniting the propellant charge therein.
Heretofore, nipples usable in conjunction with percussion caps to ignite a propellant charge in a firearm have included an elongate body having a passage extending longitudinally therethrough. Such passage generally includes a cylindrical primary chamber communicating with a cap-receiving end of the nipple and a shorter, relatively small-bore constriction chamber communicating with the gas discharge end of the nipple. Additionally, there are generally provided tapered sections adjacent the two end regions of the nipple and a steep-walled tapered section interconnecting the two chambers.
Analyzing the above features, it may be said that the primary chamber serves as an explosion chamber for the percussion cap, and the constriction chamber serves to restrict flow of particles out of the primary chamber, whereby a high gas pressure within the primary chamber occurs at the time of the percussion explosion. The tapered section adjacent the cap-receiving end of the body, by decreasing the annular end surface area of the nipple, acts to increase the pressure exertable on the percussion cap upon impact of the firearm hammer. The tapered section adjacent the gas-discharge end of the nipple, by increasing the volume of the small-bore chamber, facilitates gas flow through the small-bore chamber. The tapered section interconnecting the two chambers accommodates entry of pressured gas from the primary chamber, through the constriction chamber, and into the firearm ignition chamber.
The above-described nipple has not been entirely satisfactory in that heated gases from the detonated percussion cap tend to blow back in the direction of the cap. Such blow-back adversely effects ignition efficiency, and may present a danger to the firearm user. Blow-back of heated gases may also occur upon ignition of the propellant charge in the firearm, further diminishing the firearm performance.
In the present invention there is provided a novel nipple in which blow-back of heated cap gases is substantially eliminated. Particular features of the present invention in nipple design responsible for reduced blow-back include an enlarged primary section, and a cone-shaped section which provides entry for gases from the primary section into a constriction section. Specifically, the volume of the primary section has been enlarged about twofold over earlier nipple designs. The volume of the cone-shaped section is dimensioned to have a greater volume and a lesser axial dimension than those of the constriction section. Additionally, the end regions of the primary and constriction sections are untapered, serving to reduce blow-back from the firearm and simplifying nipple construction.
It is a primary object of the present invention to provide a nipple of greatly improved efficiency which is useful in the ignition of a powder-loaded firearm ignited by use of a percussion cap.
More specifically, it is a purpose of the invention to provide such a nipple in which the blow back of cap gases is substantially eliminated.
Another object of the invention is to provide a nipple which is simple in construction.